1. Field of the Invention
The present invention relates to a length measuring apparatus for measuring the length of an object or length between two points, or a distance measure apparatus for measuring the distance between two points on a map.
2. Description of the Related Art
An apparatus is known which rotates a rotational disc along a line connecting two points and detects the amount of rotation of the disc to thereby measure the distance or length between the two points. Such a measuring apparatus is disclosed in, for example, Japanese Patent Disclosure Nos. 61-169710 and 61-149801.
U.S. Pat. No. 3,999,198 discloses such a measuring apparatus assembled in a wrist watch.
A technique concerning a measuring apparatus assembled in a wrist watch has been also described in U.S. patent application Ser. No. 315,526 U.S. Pat. No. 4,914,831 and 373,157 filed on Feb. 24, 1989 and June 28, 1989 (Assignee: Casio Computer Co., Ltd. assignee of the present invention). This type of length measuring apparatus is used as, for example, a map meter.
This type of map meter has a scale-reduction key for inputting scale-reduction data, with which scale-reduction key a scale-reduction data (for example, x-value of 1:x) printed on a map is input. Then the map meter calculates an actual distance by multiplying the value of the scale-reduction data to the length of a path on the map along which a roller travels or rolls.
However, some maps have no indication of a numerical scale-reduction index such as, for example, 1/10000. Many of these maps have a scale indicating the scale-reduction, e.g., a scale of 1 cm representing one mile at the bottom.
To use these maps, the user of the map is required a troublesome work that he has to calculate the scale reduction value from the length of the scale of the scale reduction for the map and its length unit, and calculated into a map meter with use of a scale-reduction key.